Because ISPF does not provide true parsing, the built-in language scanner does not operate as a syntax checker. Keywords or built-in function names that are used as variables, and therefore not used in a language context, will be highlighted as keywords. For example, in context sensitive languages such as PL/I, the word 'ELSE' may be used as a variable name. ISPF treats 'ELSE' as a keyword in all cases, both for highlighting and logic determination.

In addition, the varying implementations and release schedules of the supported languages may result in keyword highlighting that does not reflect the latest version of the language.

Also, because the language scanners of edit highlighting do not provide true parsing, when an unmatched end tag is encountered and the LOGIC option is enabled, subsequent end tags might be highlighted as unmatched, even if they appear to be properly matched.